Consolidation of thermoplastic fibers into a fibrous structure such as the consolidation of polypropylene fibers for molded parts and other applications is typically accomplished by hot pressing under pressure at typically high temperatures (about 300° F. or more) and typically high pressures of (about 300 psi or more) to obtain consolidated fibrous structures having the desired performance attributes. The high temperature requirement hinders the ability to co-process the polypropylene fibers with other materials such as polymer fibers that are compromised at or above 250° F. The high pressure requirements prevent these materials from being processed in cost-effective autoclavable processes where the maximum application pressure is often about 45-100 psi. Due to the existing method of high temperature-high pressure consolidation, manufacturability of large parts requires large metal moulds which add to the cost of the machinery and finished parts significantly.
Thus, there is a need for a method that produces the same or better performance characteristics for thermoplastic fibrous layers and structures at lower temperatures, pressures, and/or dwell times than the prior art higher temperatures and pressures processes.